Centralized traffic controlling system for railroads



Ap 20, 1937.. p. F. DE LONG ET AL 2,077,619

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS 4 Sheets-Sheet 1' Filed Aug; 30, 1935 WUFEO OLMEOU n mm M o m=h%m m m m4 H mm m D. F. DE LONG ET AL CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS 4 Sheets-Sheet 2 Filed Aug. 30, 1935 o3 u l a n u x 0% $4 to 3 m .5 j I 55. n to 6 Imw.%m Q 5 E E m F m R ,mo T J E mm. mm. mm M B F n ifs. mm m I :0 96 m u m I I v T D :0 E 6 m y, R: W h I my i R I @m g Q 8 T lww L R E 3 9 3 m IIIF zo pm wzm n u @IE 8 u um o ow k KIW u n u mum 32 6pm Elwin u r llll lil L 50.52 Q. A T

Ni! n MU H U U I I I I I I I I I I I K I I SWWM U IIIIIII III April 20, 1937. D. F. DE L ONG ET AL I 2,077,619

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS I Filed Aug. so, 1935 4 Sheets-sheet 5 2% 2' O H L Q. in

mvaufons DFDe I n9 and FWBrixner FIG. Z.A.

THEIPATTORNiEY A ril 20, 1937. D. F. DE LONG ET AL 2,077,619

CENTRALIZED TRAFF-IC CONTROLLING SYSTEM FOR RAILROADS Filed Aug. 30, 1933 4 Sheets-Sheet 4 52 OFF lndicatio ns INVENTORS D FDe Long and FWBrixner THEIR ATTORNEY FIG.2.B.

, On Ind [cations Patented Apr. 20, 1937 UNITED STATES CENTRALIZED' TRAFFIC CONTROLLING SYS- TEM FOR RAILROADS Darrol F. De Long and Frederick W. Brixner, Rochester, N. Y., assignors to General Railway Signal Company, Rochester, N. Y.

Application August 30, 1933, Serial No. 687,477

15 Claims.

This invention relates to centralized trafilc controlling systems for railroads andmore particularly to the communication part of such systems,

A centralized traffic controlling system, as contemplated by the present invention, provides a means whereby railroad traffic is controlled from a central ofiice and whereby the operator at the central office may be informed concerning the location of trains and the condition of the devices of the system which are arranged to govern the movement of such trains. Such a system is supplemental to local automatic block signals to prevent unsafe train movements, improper operation of track switches or the like.

The switches and signals are distributed throughout the territory, but those located relatively near or adjacent each other as well as the apparatus provided to govern these switches and signals are conveniently referred to as comprising a field station. A communication system is provided to interconnect the central control office with the several field stations and is so organized that the operator obtains complete supervision of the various signals and switch devices at the remote stations.

The present invention is more particularly concerned with the organization of the circuits at the field station in a system of the two-wire double capacity type. By double capacity is meant that indications are transmitted during the operating cycle of the communication system during both the on and off periods, that is, during the periods when the line circuit is energized and also during the periods when the line circuit is deenergized.

In accordance with the present invention, the two-wire line circuit of the communication system connects the control ofiice and the several field stations in series. The line circuit includes a line relay and the contacts of two impulse relays at each field station. At the end field station, the conductors of the line are connected together to complete the two-wire circuit.

These two line conductors form a single circuit which is used to select a desired one of the field stations, after which the signals or switch devices at the selected station may be actuated or conditioned for governing the trafiic as determined by the manual operation in the control office. Since the present invention is not concerned with the transmission from the control office to the various field stations, which is commonly referred to as the transmission of controls, this portion of the system has been omitted from the present disclosure.

The communication system is also used to transmit indications to the control office for registering a particular station in the office and thereafter indicating the presence or absence of trains in particular track sections, the positions of track switches, as well as any other indications which may be useful in directing and supervising train movements. This particular function of the communication system is automatically effected when a new indication is ready to be transmitted to the control office and is conveniently referred to as the transmission of indications.

-The present invention is applied to a system of the coded duplex type such, for example, as disclosed in the prior application of N. D. Preston, et a1, Ser. No. 645,037 filedNovember 30, 1932, corresponding to British Patent #425,925 of 1932. In this type of system, the transmission of controls and the transmission of indications can occur on separate cycles of operation or they can occur during the same cycle of operations.

When indications are transmitted, the field station transmits a station registering code for registering this particular station in the control office. Thereafter, the particular indications, as determined by the positions of the various devices at this particular station, are transmitted by, means of additional code impulses, which register the indications in the control office by means of indicator devices such as lamps or the like associated with the sending station.

The duration or length of time during the off and on impulse periods of a cycle in the abovementioned prior application are used to form a characteristic code combination which determines the particular station to be registered in the control office and the particular indications to be transmitted after such registration. Since the present invention is more particularly concerned with the manner in which stations are allotted the use of the communication system during a cycle of operations and since it is not necessary for an understanding of the present invention to disclose the various control office circuits, that portion of the communication system located in the control office is shown in abbreviated form.

In the above-mentioned prior application Ser. No. 645,037, the look-out relay feature is disclosed, whereby only one station can actively associate itself with the communication line by picking up a lock-out relay associated with this particular station at the beginning of an operating cycle. After the cycle is once initiated in this prior system, only one station lock-out relay can be up at any one time. With this type of lock-out arrangement the stations are given preference in accordance with their geographic location, that is, when two or more stations attempt to transmit indications at the same time, the one nearest the control ofiice has preference and the others are locked out.

One feature of the present invention relates to the superiority-of-code type of lock-out. In this type of system when two or more stations have indications to transmit at the same time, the station selecting or SI relays at all of such stations are picked up and are dropped during the transmission of the station registering code until at the end of the station registering code the SI relays have all dropped except at one station. The SI relays of inferior stations are dropped out during the code transmitting portion of this cycle as determined by their particular code combinations as formed by the connections of their code jumpers.

The superiority-of-code type of lock-out arrangement has been applied to a two-wire line circuit, as for example, in the prior application of T. J. Judge, Ser. No. 635,062 filed September 27, 1932, corresponding to British Patent #419,401 of 1932. In this prior application, however, indications are not of the double-capacity type, but are only transmitted during the off (de-energized) periods of the line circuit. The present invention provides the superiority-of-code type lock-out in a two-wire system of the doublecapacity type.

Other objects and advantages of the present invention will be hereinafter set forth in the specification and claims and shown in the drawings. The characteristic features will be explained more in detail in the following description of one embodiment of the invention while the various other characteristic features and. advantages of the system comprising this invention will be in part pointed out and in part apparent as the description progresses.

In describing the invention in detail reference will be made to the accompanying drawings which illustrate in a diagrammatic manner the apparatus and circuits employed. Those parts having similar features and functions are designated by like letter reference characters generally made distinctive either by the use of distinctive exponents representative of their location or by the use of suitable preceding numerals representative of the order of their operation, and in which:

Figs. 1A and 1B illustrate a portion of the apparatus and circuits employed at a typical field station.

Figs. 2A and 2B illustrate an additional portion of the apparatus and circuits employed at the same typical field station.

Within the rectangle bounded by the dash line in the upper left-hand portion of Fig. 1A, a very small portion of the control ofiice circuits are illustrated to indicate that the two-wire line circuit is normally energized from the control office battery, and to indicate how this battery is reversibly connected to the line circuit for transmitting controls, and how the line circuit is deenergized by the operation of the line impulsing relay.

General description The operation of the circuits may be conveniently followed by placing Figs. 2A and 2B below Figs. 1A and 1B, with Fig. 13 to the right of Fig. 1A and with correspondingly numbered lines in alignment. It will be understood that the twowire line circuit extends through the other stations of the system, the connections of which are practically the same as those illustrated in the present drawings. As will be more specifically pointed out in the following description, the points of difference in the circuit connections at the different field stations are the distinctive connections of the code jumpers so that a particular field station transmits an individually distinctive code combination of impulses.

For the purpose of simplifying the illustrations and facilitating in the explanation various parts and circuits have been diagrammatically shown and certain conventional illustrations have been employed. The drawings have been made more with the purpose of making it easy to understand the principles and mode of operation rather than with the idea of illustrating the specific construction and arrangement of parts that would be employed in practice. Thus, the various relays and their contacts are illustrated in a conventional manner, the use of symbols being employed to indicate the connections to the terminals of batteries or to the sources of current instead of showing all of the wire connections to these terminals.

The symbols and indicate the positive and negative terminals respectively of suitable batteries or other sources of current, and the circuits with which these symbols are used always have current flowing in the same direction. No attempt has been made to show all of the apparatus employed or its exact arrangement at the field stations, since this may Vary to suit local conditions. The character of that portion of the control office and field station apparatus illustrated will now be considered.

Ofiice and station equipment As typical of the equipment located in the control office whereby the line circuit is energized with or impulses, a positive control re lay PC and a negative control relay NC are indi cated. Line relay F is connected in series with one wire of the two-wire line circuit and this wire is arranged to be intermittently impulsed by means of pulsing relay PL.

The communication part of the system at the field station includes a three-position biased-toneutral polarized line relay F together with its quick acting line repeating relay FP Relay F is normally positioned to the right by reason of the normally energized line wire 1 to which the terminal of control office battery B is connected. Relay FF is normally deenergized. Slow acting relays SA and SAP are provided to define the bounds of each cycle of operations. Relay SA is sufiiciently slow releasing so that it holds its armature attracted during all off periods (irrespective of the length of the off periods) except the last or change to normal period which is sufficiently long to allow relays SA and SAP to drop their contacts.

The field station includes a bank of stepping relays IV 2V 3V 4V and the associated ha1fstep relay VP For the purpose of illustrating the manner in which the long and short on and off periods of a cycle of operations are determined and provided during a cycle of operations, relays PT PF and PB are illustrated in Fig. 2A. The jumper connections illustrated in Fig. 2B determine the length of the 01f and on periods of the line circuit, as will be specifically pointed out later in the description.

For the purpose of illustrating the manner in which the stations are selectively asociated and disassociated with the line circuit during a cycle of operations, two SI relays, I81 and 2SI are shown in Fig. 1A. Relay ISI is selectively maintained energized during the off periods and relay ZSI is selectively maintained energized during the on periods of the line circuit during an operating cycle.

For the purpose of illustrating the manner in which the length of the off and on periods are checked at a particular field station to determine if the particular code being trans mitted matches the code at this particular station, relays F'I FTP BT and ET? are provided. Relay F'l 'checks the timing of the on periods and relay BT checks the timing of the off periods, with the corresponding repeating relays FTP and B'IP cooperating in a manner which will be fully pointed out later.

A change repeating relay CHP is employed at each field station in connection with the indication circuit to determine when this field station is to transmit new indications. This relay is indicated with its control circuit omitted, but it will be understood that relay CHP automatically registers a change in the condition of any device such as the track section, switch or signals and stores such a condition until an operating cycle has taken place to transmit indications of such condition to the control office. The circuit arrangement for relay CHF is such that it is picked up to start a cycle of operations and is dropped at some point during this cycle so that it may be again energized when additional indications are to be transmitted. The circuit arrangement for relay CHP may be of the type fully disclosed in the patent to De Long et al., No. 1,852,402 issued April 5, 1932, and to simplify the present disclosure it will not be explained in detail, but it may here be considered that its control wire 35 corresponds to wire 33 in the above mentioned patent.

It is believed that the nature of the present invention, its advantages and characteristic features may be best understood with further description being set forth in the manner of operation. I

Operation In the present system the single line circuit,

consisting of the two line wires 1 and 9 extending from the control office to all field stations, is normally energized by a steady flow of direct current and the system may be initiated into a cycle of operations either at the control office or at any field station by means arranged to open this line circuit. The system then operates through the cycle, which consists of a definite number of impulses applied to the line at the control onice and during this cycle new controls may be transmitted from the control office to any one field station, new indications may be transmitted from any one field station to the control ofiice, or duplex transmission may be accomplished whereby both controls and indications are transmitted between the same or different field stations and the control ofiice.

It is evident that in accomplishing duplex transmission over a single circuit, two distinctive code arrangements cannot be formed by selecting the character of the impulses alone, and consequently the system is so organized that codes for outbound transmission are formed by selecting the polarity of the impulses. As above mentioned, the manner in which this portion of the system operates is immaterial to an understanding of the present invention, therefore, it is not considered necessary to illustrate or describe the circuits employed for the transmission of controls.

The code arrangement for inbound transmission is formed by selecting the lengths of the energized and deenergized periods of the line, which for convenience are referred to as the on and off periods respectively.

In describing the operation of the system in detail, it is considered sufficient to briefly outline the functions of such parts as have been described in detail in previously mentioned applications. Also, in describing in detail theoperations which will be considered as typical of the novel features of the present invention, it. is convenient to discuss separately the groups of such operations in detail under the headings as indicated.

Normal period of rest With the communication system, with which this invention is concerned, at rest, all of the relays illustrated in the drawings are in their normal or deenergized positions except the line relays and relay PT of Fig. 2A. The control line conductor is normally energized over a circuit extending from the terminal of battery B in the control oiiice, front contact 26 of relay PC, back contact 21 of relay NC, winding of relay F, back contact 28 of relay PL, line conductor I, winding of relay F back contact 62 of relay PF back contact 63 of relay PB line conductor 64 which extends through the other field stations in series, line conductor 9 returning through the other field stations in series, back contact 29 of relay NC and front contact 36 of relay PC to the terminal of battery B. Relay F in the control oifice is of the neutral type and normally its, contacts are in their picked up positions. Relay F at the field station has its polar contacts positioned to the right as indicated.

Relay PT is energized over a circuit extending from contact 290 of relay F in its right hand position, back contact Zfll of relay SAP and wind ing of relay PT to Operation of stepping relays The stepping relays in the control office have not been illustrated and the stepping relays at the typically illustrated field station have only a portion of their control circuits shown. The operate ing circuits for these stepping relays have been omitted, but for the purpose of disclosing the present invention it will be assumed that they function in the same manner as disclosed in the above mentioned prior application Ser. No. 635,062. As in Ser. No. 635,062, the operation of the present system consists of cycles, each comprising a starting or momentary deenergized period of the line, followed by a conditioning or energized period of the line. Then follows a series of deenergized and energized periods of the line of variable lengths, as determined by the code being transmitted. For convenience, the deener gized periods of the line are referred to as oil periods and the energized periods of the line are referred to as on periods.

The stepping relays are successively picked up during the off periods of a cycle (after the start period) and the VP relay is shifted during the on periods of a cycle. More specifically, relay VP is picked up during the conditioning on period and stuck up until the next on period. Relay IV is picked up during the first off period, relay VP is dropped during the first on period and relay 2V is picked up during the second oiT period. Relay VP is picked up during the second on period and stuck up until the next on period. Relay 3V is picked up during the third off period, relay W is dropped during the third on period and relay 4V is picked up during the fourth off period. The stepping relays IV to 4V inclusive, are stuck up, when picked up, until the clearing out off period at the end of the cycle.

It will be understood that contact I27 of relay FP of Fig. 1A repeats the off and on periods of the line during impulsing. This contact and the dotted line leading to the bracket embracing relays VP to 4V inclusive, of Fig. 1B control the operation of these relays as above described and in the same manner that contacts I28 and I29 of relay FP in Fig. 2- of Ser. No. 635,062 control the operation of similar relays in this prior application.

The timing of the impulses (on periods) and the spaces between impulses (01f periods) will now be briefly pointed out, reference being made to British Patent No. 419,401 for a detailed explanation of this operation. The ofiice opens the line at the end of an on period to mark the beginning of the next off period, by picking up relay PL. 'In response to the open line condi tion, relay F drops, then relay FP drops, then. the stepping relay picks up, then relay E (shown in the above mentioned British patent but not shown in the present disclosure) drops, then relay PL drops and closes up the line to mark the beginning of the next on period. In response to the closed line condition, relay F picks up, then relay FP picks up, then relay VP shifts (picks up or drops depending on whether it is down or up), then relay E picks up, then relay PL picks up and opens the line to mark the beginning of the next off period. This operation of course makes the impulses and the time spaces of uniform length. During this application of the im pulses to the line by the'ofiice apparatus, a transmitting station modifies these impulses and the time spaces between, to form codes by varying their lengths.

Automatic start and conditioning In connection with the present disclosure, consideration will be made to the manner in which indications alone are transmitted from a field station to the control office, since the circuit operation as far as the present invention is concerned is the same when indications are transmitted during the same cycle that controls are transmitted outbound.

It will be assumed that relay CHP of Fig. 1B is picked up in response to a change in condition at the associated field station such as the occupancy of a track section or a movement of a traffic controlling device. A circuit is now closed for picking up relays I31 and 281 extending from front contact 65 of relay CHP conductor 80, back contact 61 of relay SAP, and the upper windings in series of relays ISI and ZSI to Relay ISI closes a stick circuit for itself which is effective until relay I V is picked up and which extends from back contacts 48, M and 42 of relays 3V 2V and l V respectively, conductor 8|, front contact 43 of relay ZSI front contact 44 and lower winding of relay lSI to A circuit is now closed for picking up relay FT which extends from front contact 45 of relay 281 back contact '55 of relay FP and winding of relay FT to A circuit is also closed for picking up relay P13 which extends from back contact 22 of relay lV back contact 203 of relay VP conductor 82, front contact 204 of relay PT front contact 205 of relay 281 front contact 206 of relay I S1 back contact 207 of relay FF and winding of relay PB to Relay PB closes a stick circuit for itself, extending from front contact 208 of relay PT front contact 209 and winding of relay PB to The opening of back contact 63 of relay PB deenergizes the line circuit which allows relays F and F to drop to their neutral positions. The dropping of relay F in the control office effects the picking up of relay STR, which in turn causes the dropping of relay PC and the picking up of relay NC for reversing the connection of battery B to the line circuit. The picking up of the start relay STR in the control oflice, which controls the shifting of the PC and NC relays just mentioned, is effective to initiate the cycle of stepping operations in the control office. The operation of relay STR and the manner in which the line circuit is impulsed by relay PL is fully set forth in the above mentioned prior application Ser. No. 645,037 and may be briefly explained as follows:

The dropping of relay F in response to the field station opening the line to start a cycle of operations, closes a pick-up circuit for relay STR (not shown) which extends through a back contact of the SA relay and a back contact of the F relay in the olhce. Relay STR is then stuck up until the end of the cycle. With relay STR up, the circuit shown in the upper left hand portion of Fig. 1A of the present disclosure is shifted from the PC to the NC relay so that relay PC drops, relay NC picks up and remains up throughout the cycle. The SA and the SAP relays in the office (not shown) pick up in response to the picking up of relay NC and the stepping relays in the oflice (not shown) operate through their cycle as previously mentioned. Relay PL is controlled by the response of the stepping relays and opens the line at back contact 28 (corresponding to back contact 3 in application 635,062.) when the VP relay shifts during each on period and to close the line at back contact 28 when a stepping relay picks up during each off period. During this impulsing, the control ofiice normally applies a comparatively long on period to the line which can be changed to a short on or not as determined by the station which is transmitting. Similarly, the omce normally applies a comparatively short off period to the line circuit which can be changed to a long off or not,'as determined by the field station which is transmitting, all of which will be pointed out in detail in the following description.

The picking up of relays I81 and 281 closes a stick circuit for relay PT which is independent of the above described pick-up circuit for this relay through back contact 251 of relay SAP which stick circuit is completed before relay F drops to open the normally energized pick-up circuit of relay PT. This stick circuit extends from through either front contact 2H) or 2 of the relays I81 and 281 respectively, front contact ZlZ of relay PT back contact 2l3 of relay PB and winding of relay PT to At the time relay F opens its contact 20, the above described pick-up circuit for relay P1 is deenergized, but relay PT momentarily remains in its picked up position until the opening of back contact 2l3 of relay PB which opens the stick circuit of relay PT allowing this relay to drop.

The opening of front contacts 204 and 208 of relay PT opens the above described pick-up and stick circuits of relay PB which allows this relay to drop. The dropping of back contact 63 of relay 'PB again energizes the line circuit to mark the end of the start off period and the beginning of the conditioning on period. During this conditioning on period, the line repeating and the slow acting relays in the control office are conditioned, as disclosed in the above mentioned prior application Ser. No. 645,037. The line relays together with the line repeating and slow acting relays at all of the stations are likewise conditioned during the conditioning on-' period.

The dropping of relay PC and the picking" up of relay NC in the control oflice, as previously mentioned, has the effect of energizing line conductor I with a potential (when relay PB closes its back contact 63) which is effective to position relay F to the left and to pick up relay F in the office. A circuit is now closed for picking up relay FP which extends from contact I22 of relay F in its left hand dotted position and winding of relay FP to A circuit is closed for picking up relay PT which extends from front contact 2I4 of relay FP back contact 2I3 of relay PB and winding of relay PT to Relay PT again closes the above described stick circuit for itself including front contacts 2I0 and 2H of the SI relays, which stick circuit is independent of front contact 2I4 of relay FP A circuit is closed for picking up relay F'IP which extends from front contact 45 of relay 2SI front contact 46 of relay FP front contact 41 of relay FT conductor 83 and winding of relay FTP, to Relay FTP closes a stick circuit for itself extending from front contact 48 of relay FT conductor 84, front contact 49 and winding of relay FTP, to

A pick-up circuit is closed for relay BT extending from front contact 3| of relay ISI front contact 32 of relay FP conductor 85 and winding of relay BT, to The picking up of relay FP closes a stick circuit for relay 2SI which is effective before relay SAP picks up and opens its back contact 61 to open the pick-up circuit of relay 2SI This stick circuit extends from front contact 33 of relay FP front contact 34 of relay 2SI front contact 36 of relay ISI and lower winding of relay 2SI to The opening of back contact 46 of relay FP opens the circuit of relay FT and'this latter relay drops after a time interval which is determined by its slow acting characteristics. The opening of contacts 41 and 48 of relay FT deenergiZes relay FTP and this relay is dropped in turn.

The closure of front contact I23 of relay FP closes an obvious pick-up circuit for relay SA and the closure of front contact I24 of relay SA closes an obvious pick-up circuit for relay SAP During the impulsing of the line circuit and the consequent operation of contact I22 of relay F relay FF is energized when contact I22 is in its left hand dotted position and when this contact is in its right hand position, the circuit forenergizing relay FP extends through front contact I25 of relay SAP The positive energy provided from through front contact I26 of relay SAP which extends through the front or back contact I2'I of relay FP is for the purpose of controlling the pick-up and stick circuits of the stepping and half step relays, such circuits being completely shown in the above mentioned prior application Ser. No. 635,062. As above mentioned, relay VP is picked up during the conditioning on period.

'An additional stick circuit is now closed for relay "281 which is independent of front contact 33 of relay FP and which extends from front '5 contact 68 of relay VP back contact 69 of relay 2V conductor 36, front contact 34 of relay 281 front contact 36 of relay ISI and lower winding of relay 2SI to Transmission of sending station code It will be assumed that the typical field station illustrated applies the following codeto the line:-- Step 1-long off, short on. Step 2-Short off, long on. Step 3-sh0rt 01f, short on. This is determined by the first step code jumpers 23I and 24! being connected to the second step code jumpers 232 and 242 being disconnected from and the third step code jumpers 233 and 243 being disconnected from and connected to respectively, all as illustrated in Fig. 2B. It will be understood that this code is transmitted during a cycle, during which relays SA and SAP are picked up.

The code jumpers illustrated in Fig. 1B must correspond to those of Fig. 213 so that this station can check the code combination applied to the line by itself and by other stations to determine if its code is superior or inferior. Thus, the first step code jumpers I3I and MI are connected to the long off and short on buses respectively. The second step code jumpers I32 and I42 are connected to the short off and long on buses respectively. The third step code jumpers I33 and I43 are connected to the short off and short on buses respectively. It is to be understood that there must be a similar correspondence at other stations between the code jumpers, similar to those of Fig. 2B and the code jumpers, similar to those of Fig. 1B.

The end of the conditioning on period, and the beginning of the first off period is marked by the control office circuits functioning to pick up relay PL. This is due to relay VP in the office picking up (in synchronism with relay W at the station) and indirectly controlling the energization of relay PL as clearly disclosed in application 635,062. The picking up of relay PL opens the line at back contact 28. This drops relay F to its neutral position, which in turn drops relay FP when contact I22 leaves its actuated position. A circuit is now closed for picking up relay IV which circuit is not shown in the present drawings.

Since it is assumed that the No. 1 off period is long, as determined by jumper 23I being connected to a circuit is now effective to pick up relay PB which extends from long off conductor 220, jumper 23I, front contact 22I of relay IV back contact 222 of relay 2V front contact 203 of relay 1P conductor 82, front contact 204 of relay PT front contacts 205 and 206 of the SI relays, back contact 201 of relay FP and winding of relay P25 to Since relay ET is picked up at this time, the above described stick circuit for relay PB including front contact 208 of relay PT is again established. A circuit is closed for picking up relay FT which extends from front contact 45 of relay 2SI back contact 46 of relay FF and winding of relay FT to The picking up of relay PB opens the circuit of relay PT at back contact 2I3, allowing this latter relay to be released. The opening of contacts 204 and 208 of relay PT opens the pick-up and stick circuits of relay PB which drops after a comparatively long interval of time due to the slow acting characteristics of this relay. This slow release of relay PB maintains the line circuit open at back contact 63 for a comparatively long interval for providing the long off assumed for this portion of the code.

When relay FP closes its back contact 32 a circuit is established for picking up relay BTP extending from front contact 3| of relay ISI back contact 32 of relay FP conductor 81, front contact 3'! of relay BT and winding of relay BTP to The closure of front contact 33 of relay BTP establishes a stick circuit for this relay extending from front contact 39 of relay BT front contact 38 and winding of relay BTP to The opening of front contact 32 of relay F'P deenergizes the winding of relay BT so that this relay drops during the long off period provided by the delayed dropping of relay PB The dropping of relay BT opens the pickup and stick circuits of relay BTP allowing this latter relay to be released during the first off (long) period.

The closure of back contact 63 of relay PB closes the line circuit at the field station. It will be understood that the ofiice attempts to energize the line before relay P13 has dropped its contacts, in an attempt to provide a normally short off period. Therefore, since the line circuit is now closed at the field station and in the control ofiice, it is energized. This results in picking up relay F which in turn picks up relay FP over the previously described circuit. It will be understood that during the interval of time when front contact I23 of relay FP is open, relay SA does not have time to drop its contacts due to its slow acting characteristics. The picking up of relay FP during the first on period again picks up relay PT over the previously described circuit including front contact 2H4 and relay PT is stuck up as before. Relay V1?" is dropped during the first on period.

The timing relays in the control ofiice open the 40 line circuit to terminate each on period after a comparatively long interval of time. Since it is assumed that the first on period is short, as determined by code jumper 2M being connected to the field station opens the line before the control office measures off its predetermined time interval. This is accomplished by the picking up of relay PF immediately after relay VP drops, over a circuit extending from short on conductor 23!], jumper 24I, front contact 223 of relay I V back contact 224 of relay 2V back contact 225 of relay V1 conductor 88, front contacts 226 and 22'! of the SI relays, front contact 228 of relay PP and winding of relay PF to Relay PF opens the line at its back contact 62 to mark the end of the first on period and the beginning of the second off period.

Referring back to the first on period, relay FTP is picked up and stuck up over the previously described circuits including front contacts 4'! and 48 of relay FT During the first on period relay ET is again picked up over its previously described pick-up circuit in readiness to check the length of the next (second) off period. The opening of the line at the end of the first on period causes relay F to drop its contacts, which in turn drops relay FP after which relay 2V is picked up. Relay PF is dropped in the second off period by the opening of front contact 228 of relay F'P in readiness to be picked up or not, as determined by the second on jumper connection. Relay FT due to its slow acting characteristics, does not have time to drop during the No. 1 on period which was assumed to be of short duration and it remains picked up throughout the succeeding (second) off period over the circuit including back contact 46 of relay FP Relay B'IP is again picked up and stuck up during the second off period by means of its previously described pick-up and stick circuits. The second off period is assumed to be short (normal duration) as determined by the control office closing up the line at back contact 28 of relay PL after the proper time has been measured off by the ofiice timing relays. This 0 period is not made abnormally long, because jumper 232 of Fig. 23, selected by front contact 234 of relay 2V is disconnected from conductor 220 which leads to During this comparatively short off period relay BT does not drop its contacts, because front contact 32 of relay FP does not remain open for a sufliciently long interval of time to allow relay BT to drop its armature. When the office closes up the line to mark the end of the second off period and the beginning of the second on period, the closure of front contact 32 of relay FP reenergizes relay BT before it has had time to drop its contacts.

Relay VP is picked up during the second on period. Since code jumper 242 of Fig. 23, as

selected by front contact 244 of relay 2V is dis connected from conductor 230, the second on period will be normally long. This is determined by the transmitting field station not opening the line as before, but waiting for the control office to open the line. During the second on period relay FT being deenergized at back contact 46 of relay FP has time to drop its contacts which opens the pick-up and stick circuits of relay FTP allowing this relay to drop its contacts in turn.

When the control office opens the line to mark the end of the second on period and the be ginning of the third 01f period, relays F and FP are dropped and relay 3V is picked up. Relay FT is again picked up over the previously described circuit including back contact 46 of relay FP Since it is assumed that the third off period BT does not have time to drop its contacts and relay B'I'P remains stuck up. The third off period is short because the line is immediately energized when the control office closes the line to mark the end of the third off period and the beginning of the third on period. This is due to jumper 233, as selected by front contact 236 of relay 3V being disconnected from conductor 220 so that the field station does not interrupt the line circuit but allows the control office to energize it in a normally short interval of time.

The energization of the line picks up relays F and FF and. drops relay VP Relay FTP is again picked up and stuck up by means of the previously described circuits. Since jumper 243, as selected by front contact 246 of relay 3V is connected to on conductor 2311, relay PF is picked up over a circuit extending from on conductor 23!], jumper 243, front contact 246 of relay 3V back contact 247 of relay 4V back contact 225 of relay VP conductor 88, front contacts 226 and 221 of the SI relays, front contact 228 of relay FF and winding of relay PF to The opening of back contact 62 of relay PF opens the line at the field station before waiting for the control office to open' it, which provides an abnormally short third on period. Relay FT is not dropped during the third on period because back contact 46 of relay FF is closed up for reenergizing relay F'I before it has is of normally short duration, relay" time to drop its contacts. The opening of the line at the end of the third on period marks the beginning of the fourth off period and permits relays F and FF to drop.

' It will be understood that this operation may be continued for as many steps as required to provide the code combination for registering the transmitting station in the control office. It will also be understood that additional steps will be provided for selecting the short and long on and off code combinations by way of indication relay contacts or the like, instead of jumpers for providing the code which transmits the required conditions from the registered station to the control ofiice.

The above explanation sets forth the manner in which the typical field station illustrated applies its code combination of long and'short off and on periods as determined by the connections of its jumpers 23I, 232, 233, MI, 242 and 243. The manner in which the transmitting station is registered in the control ofliceby the reception of this code combination may be, for example, as fully disclosed in the above mentioned prior application Ser. No. 645,037. From the above example it will be obvious that alternate codes can be applied at each step by the alternate connection (or disconnection) of the jumpers so that all stations can provide code combinations which differ from each other.

Plurality of stations simultaneously transmitting In the event that there are two or more stations with new indications to transmit when the system is at rest (SAP relays down), there will be two or more change repeating relays up which causes the SI relays at the associated stations to be picked up and stuck up in a manner obvious from the above explanation of this operation. They remain stuck up throughout the conditioning period of the cycle and are dropped out at the inferior stations during the succeeding off and "on periods as determined by the correspondence between the code jumpers such as I3I, I32, I33, I4I, I42 and I43 of Fig. 1B and the 9 length of the corresponding off and on periods of the cycle.

After the last station selecting step has been taken, only one pair of SI relays such as relays ISI and 231 will remain picked up during the remainder of the cycle. Only at the station at which these two relays remain up are the succeeding steps of the cycle effective to transmit code impulses in accordance with the positions of the various devices at this particular station. At those stations which are dropped out due to inferior codes, the indication circuits are disconnected from the PB and PF relays. The on in dication circuits are disconnected from the PF relays at contacts similar to 226 and 221 of re- 60 lays 2S1 and ISI respectively. The off indication circuits are disconnected at contacts similar to 265 and 266 of relays 2S1 and ISI The PT relays at those stations are picked up but have no effect on the other circuits since the cir- 65 cuits leading off to the left from contacts 208 and 264 are incomplete.

Dropping out inferior stations main actively associated with the line during this first off period. This is because the FP relays open their front contacts similar to 32 for a sufliciently long interval of time to drop the BT relays and thereafter the BTP relays at these stations, so that a selecting stick circuit is maintained for the SI relays over a circuit similar to that extending from back contacts 40 and M of relays 3V and 2V respectively, front contact 42 of relay IV jumper I3I, bus I36, back contact I34 of relay BTP conductor 8|, front contacts 43 and 44 of relays ZSI and ISI respectively and lower winding of relay ISI to It is obvious that the 2SI relays are stuck up through front contacts similar to 33 of relay FP during the on period (first) following the first off period of the cycle.

It will be apparent from the previous explanation that relays such as BTP are down throughout an on period when the previous off pe-' riod is long and these relays are up throughout an on period when the previous off period is short. Similarly the relays similar to FTP are down throughout an off period when the previous "on period is long and they are up throughout an off period when the previous on period is short.

All stations actively associated with the line circuit during the first off period have their BTP relays down throughout the first on period. This is because the first off period is sufficiently long to drop the BT relays, due to the front contacts similar to 32 of the FP relays being open for a comparatively long interval. This dropping of the BT relays opens the pick-up and stick circuits of the BTP relays at all transmitting stations, allowing these latter relays to be dropped. At the beginning of the first on period the picking up of the FP relays will not drop the SI relays at stations with a No. 1 long off code due to a circuit similar to that extending from back contact 40 of relay 3V back contact 4| of relay 2V front contact 42 of relay IV jumper l3I, bus I36, back contact I34 of relay BTP conductor 8|, front contact 43 of relay 2SI front contact 44 and lower winding of relay ISI to At those stations having the first off jumper similar to I 3| connected to the short off bus similar to I31, the opening of front contact similar to I34 of the BTP relays opens the selective stick circuits of the ISI relays and since the FP relays disconnect from the stick circuits at back contacts similar to 33, there are no energizing circuits to hold these ISI relays in their picked up positions. The dropping of the ISI relays opens up the stick circuits of the ZSI relays at front contacts similar to 36 and consequently both SI relays are dropped at inferior stations.

In the above example the second off period is short. At those stations with a jumper connection similar to I32 of Fig. 1B, the SI relays will be stuck up over circuits similar to that ex tending from back contact 40 of relay 3V front contact 4| of relay 2V jumper I32, bus I31, front contact I34 of relay BTP and over the remainder of the previously described circuit through the lower windings of the ISI relays. Therefore, the ISI relays will remain stuck up during the second on period after the FP relays open their back contacts similar to 33, at those stations with a jumper connection similar to I32.

Still assuming that one or more other stations are using the line during this cycle, then if one of these other stations transmits a second long 01f indication those stations having a short off code combination for this step are dropped out because the long off is superior to the short 5 off. Such a long off combination keeps the line circuit deenergized long enough to drop the BT and BTP relays for switching the contacts similar to I34 from the short off bus to the long off bus. Therefore, at those stations with a second long off code the selective stick circuits of the ISI relays are completed through back contacts similar to I34 of the BTP relays. At those stations having a second short 01f code these selective stick circuits are not completed because the BTP relays at all stations drop and by the opening of front contacts similar to I34, the selective stick circuits of the SI relays at those stations where the jumpers similar to I32 do not connect to the long off buses are interrupted.

It is believed that the above examples of the manner in which the SI relays are maintained in their energized positions at superior stations and dropped at inferior stations, as well as the explanation of the checking of the long and short off indications in connection with the first two codes, are suilicient to give an understanding of the operation of this feature of the invention at additional steps of the cycle.

' It will be recalled that the assumed code combination provides a first short on and a second long on. It will now be explained how these two combinations are checked at the field stations so that those stations with a short on combination remain on the line in preference to those with a long on combination. The FT and FTP relays check the timing of the on periods of the cycle. Relay FT is not dropped during a short on" period because back contact 46 of relay PF is closed at the end of the on period in a comparatively short interval of time after this contact is opened at the beginning of the on period.

It will be recalled that relay FT remains picked up throughout the second off period over a circuit through back contact 46 of relay FP and that relay FTP is picked up during the first on period. Since relay FT is not dropped, relay FTP remains stuck up through the succeeding (second) off period over a circuit including 50 front contacts 48 and 59 of relays FT and FTP. This results in relay FTP remaining picked up throughout the second off period because the first on period is of short duration.

The above discussion relating to relays FT and FTP also applies to similar relays at other stations which are transmitting. At those stations having a code jumper connection similar to NH the 251 relays will remain stuck up during the second off period over a circuit similar to that extending from back contact 68 of relay VP back Contact 10 of relay 3V front contact ll of relay [V jump-er 14], bus 12, front contact 13 of relay FTP conductor 86, front con- 65 tact 34 of relay 2SI front contact 36 of relay I8 and lower winding of relay 231 to It will be obvious that relay lSI remains stuck up during the second oif" period by way of the previously described circuit to at back con- 70 tact 33 of relay PP and this of course applies also to all stations which are transmitting.

At those stations where the jumpers similar to I41 are connected to the long on buses similar to 14, the opening of back contacts similar to I75 13 of relay FTP interrupts the above described stick circuits for the 281 relays and these relays are released.

The second long on code combination causes the dropping of the FT relays because the FP relays have their back contacts similar to open 5 for a sufficient interval of time to allow the FT relays to drop. This drops the FTP relays by opening their pick-up and stick circuits during the second on period. At those stations where the jumpers similar to. I 42 connect to the long 10 on buses, the selective stick circuits of the 251 relays are completed over circuits similar to that extending from front contact 68 of relay VP front contact 69 of relay 2V jumper I42, bus 14, back contact 13 of relay FTP conductor 15 86, front contact 34 of relay 261 front contact 36 of relay 1 S1 and lower winding of relay 231 to The 1531 relays are stuck up during the off period over a circuit similar to that extending through back contact 33 of relay FP front contacts 43 and 44 of relays 2SI and ISI respectively and the lower winding of relay ISI to If there is a station transmitting a second short on indication, then the station or stations with 25 a long second on code combination are dropped out. This is because the line is not energized for a sufiicient interval of time to drop the FT and FTP relays. Therefore, at those stations where the jumper similar to I42 is connected to the short 30 on buses, the selective stick circuits of the 281 relays are completed through the front contacts similar to 13 of relay F'IP At those stations with a long on code combination the jumpers similar to I42 are connected to the back contacts 35 similar to 73 of relay FTP by way of the long on buses, so that the selective stick circuits of the 281 relays at these stations are incomplete because the FTP relays do not drop at these stations. 40

It is believed that the above examples relating to the checking of both a short and a long on" code combination and the manner in which those stations with long on combinations are dropped out when the system transmits short on com- 45 binations at particular steps is sufiicient to indicate how this portion of the invention operates for additional steps.

When the system takes the next step after the station selecting step by picking up relay 4V permanent stick circuits are provided for the SI relays. The permanent stick circuit for relay 281 extends from front contact 15 of relay 4V conductor 86, front contact 34 of relay 2SI front contact 36 of relay 181 and lower winding of relay 2SI to The permanent stick circuit for relay ISI extends from front contact 16 of relay 4V conductor 8i, front contact 43 of relay 281 front contact 24 of relay ISI and lower winding of relay ISI to It will of course be understood that when the stepping relays are dropped at the end of the cycle these permanent stick circuits are deenergized so that the SI relays are restored to normal.

After the individual station has been selected by dropping out all SI relays except those associated with the most superior calling station as above discussed and the registration of this station in the control office as disclosed in the above mentioned prior application Ser. No. 645,037, ad- 7 ditional code impulses are transmitted to the control ofice as determined by the conditions of the various devices at the calling station. The manner in which this operation is effected, as well as the manner of restoring the system to normal 7 inferior station thereafter opening said line during said operating cycle.

9. In a centralized trafi'ic controlling system for railroads, a control office and a plurality of field 5 stations, a line circuit connecting said ofiice with said stations, means in the control office for applying normally time spaced impulses of normal length to said line circuit, code forming means at each of said stations for at times varying the lengths of said impulses and said time spaces between said impulses, a first station selecting relay at each station selectively controlled by said time spaces, a second station selecting relay at each station selectively controlled by said impulses, and means controlled by said relays in combination for selectively controlling said code forming means.

10. In a centralized traflic controlling system for railroads, a line circuit connecting a control office and .a plurality of field stations, means at the control office for applying uniformly time spaced impulses of uniform length, code transmitting means at each station operable to change the length of selected ones of said impulses and said time spaces in accordance with a distinctive code call for that station, coderesponsive means at each station selectively controlled by the varied lengths of said impulses and said time spaces for rendering said code transmitting means ineffective at that station whenever the variation in lengths of said impulses and said time spaces fail to match the distinctive code call for that stae tion, .and means in the control office responsive to the varied lengths of said impulses and said time spaces to register the resulting code call.

11. In a centralized traffic controlling system for railroadsa line circuit connecting a control ofiice and a plurality of field stations, means at the control ofiice for applying a series of uni- 40 formly time spaced impulses of uniform length, code transmitting means at each station at times operable to selectively shorten the length of said impulses and to selectively lengthen the duration of said time spaces in accordance with a distinctive code call for thatstation by opening and closing said line circuit, code responsive station selecting means at each station selectively controlled by the varied lengths of said impulses and said time spaces on said line circuit for rendering said code transmitting means inefiective at that station whenever the variation in lengths of said impulses and said time spaces fail to match the distinctive code call for that station, and means in the control ofiice responsive to the varied lengths of said impulses and said time spaces to register the resulting code call, whereby the code responsive station selecting means at only one station is conditioned for the selection of that station at the end of said series and the corresponding code call for that station is registered in the control office.

12. In a centralized traffic controlling system for railroads, a control ofiice and a plurality of field stations, a line circuit connecting said ofiice with said field stations, means in the con-' trol ofiice for applying a plurality of series of normally time spaced impulses of normal length 60 said line circuit, means for simultaneously recording at a plurality of stations the condition that indications await transmission to said oflice from said stations, means at each station responsive to said simultaneous recording for selecting said stations in rotation by modifying said series of impulses to form a code of variably time spaced impulses of variable length over said line circuit characteristic of that station, and means at each station controlled by the length of the impulses of each series characteristically modified to form a code for determining the order of selection for that station.

13. In a centralized traffic controlling sys tem for railroads, a control office and a plurality of field stations, at line circuit connecting said office with said field stations, means in the control ofiice for applying a plurality of series of normally time spaced impulses of normal length to said line circuit, means for simultaneously recording at a plurality of stations the condition that indicationsv await transmission to said ofiice from said stations, means at each station responsive to said simultaneous recording for selecting said stations in rotation by modifying said series of impulses to form a code of variably time spaced impulses of variable length over said line circuit characteristic of that station, and means at each station controlled by the length of the spaces between impulses and by the length of the impulses of each series characteristically modified to form a code for determining the order of selection for that station.

14. In a centralized trafiic controlling system for railroads, a control oflice and a plurality of field stations, a line circuit connecting said ofiice with said field stations, means in the control office for applying a plurality of series of normally time spaced impulses of normal length to said line circuit, means for simultaneously recording at a plurality of stations the condition that indications await transmission to said oflioe from said stations, means at each station responsive to said simultaneous recording for selecting said stations in rotation by modifying said series of impulses to form a code of variably time spaced impulses of variable length over said line circuit characteristic of that station, and means at each station controlled by the length of the spaces between impulses and by the length of the impulses of each series characteristically modified to form a code for determining the order of selection for that station, said means being responsive to a change in the timing order of said impulses for changing said order of selection.

15. In a centralized traffic controlling system for railroads, a control office and a plurality of field stations, a line circuit connecting said oiiice with said stations, means in the control office for applying a plurality of series of normally time spaced impulses of normal length to said line circuit, station selecting means at each station, a step-by-step mechanism at each station for selecting a plurality of code connec tions, means controlled by any series of time spaced impulses on said line circuit for advancing said mechanism through an operating cycle, means at each station for modifying said series of impulses to form a code of variably time spaced impulses of variable length transmitted over said line circuit characteristic of that sta tion, and means at each station controlled by the length of said impulses and the succeeding time spaces of any particular series of impulses for energizing said station selecting means only at the station where the selected code connections correspond to the lengths of said impulses and the time spaces between said impulses.

DARROL F. DE. LONG. FREDERICK W. BRIXNER.

at the end of each cycle, is immaterial to an understanding of the present invention and is not illustrated but may be accomplished, for example, in the same manner as disclosed in the above mentioned application, Ser. No. 645,037.

Having thus shown and described a centralized traffic controlling system for railroads as one specific embodiment of the present invention, it is desired to be understood that this form is selected to facilitate in the disclosure of the invention rather than to limit the number of forms which it may assume and it is further to be understood that various modifications, adaptations and alterations may be applied to the specific form shown to meet the requirements of practice without in any manner departing from the spirit or scope of the present invention except as limited by the appended claims.

Having described our invention, we now claim:

1. In a centralized traflic controlling system for railroads, a control ofiice and a plurality of field stations, a line circuit connecting said ofiice with said stations, means in the control ofiice for applying time spaced impulses of current to said line circuit, code selecting means at each station operable to selectively change or leave unchanged the length of said impulses and the time spaces between said impulses, and means at each of said stations responsive to the code formed by said impulses and said time spaces on said line circuit only when such code corresponds to the code formed by said code selecting means at that station.

2. In a centralized trafiic controlling system for railroads, a control office and a plurality of field stations, a line circuit connecting said office with said stations, means in the control ofiice for applying impulses of current of uniform length to said line circuit separated by uniform time space intervals, means at .each station for at times shortening the length of selected ones of said impulses, and means at each of said stations distinctively responsive to the length of said impulses.

3. In a centralized traffic controlling system for railroads, a control office and a plurality of field stations, a line circuit connecting said office with said stations, means at the control office for applying impulses of current of uniform length to said line circuit separated by uniform time space intervals, means at each station for at times shortening the length of selected ones of said impulses, means at each station for at times extending selected ones of said time space intervals, and means at each of said stations distinctively responsive to the resulting lengths of said impulses and said time space intervals on said line circuit.

l. In a centralized traffic controlling system for railroads, a control office and a plurality of field stations. a line circuit connecting said office with said stations, means in the control ofiice for applying normally time spaced impulses of normal length to said line circuit, a plurality of stepping relays at each field station operated sequentially by said impulses, means at each station controlled by the associated stepping relays for selectively opening said line circuit during a time space period between said impulses for extending such period, means at each station controlled by the associated stepping relays for selectively opening said line circuit during an impulse period, means at each station operable to close said line circuit after said time space has been abnormally extended, and means at each station responsive only to an abnormally shortened impulse period.

5. In a centralized trafiic controlling system for railroads, a control office and a plurality of field stations, a line circuit connecting said ofiice with said stations, means in the control oifice for applying normally time spaced impulses of normal length to said line circuit, a plurality of stepping relays at each field station operated sequentially by said impulses, means at each station controlled by the associated stepping relays for selectively opening said line circuit during a time space period between said impulses, means at each station controlled by the associated stepping relays for selectively opening said line circuit during an impulse period, means'at each station operable to close said line circuit after said time space has been abnormally extended, means in said oifice operable to open said line circuit after said impulse period has been abnormally shortened, and means at each station responsive only to an abnormally extended time space and an abnormally shortened impulse period.

6. In a centralized traific controlling system for railroads, a control office and a plurality of field stations, a line circuit connecting said ofiice with said stations, means in the control office for applying normally time spaced impulses of normal length to said line circuit, means at each of said stations for at times conditioning said line circuit with a superior condition during selected ones of said impulses whereby the lengths of selected impulses .are changed from normal to abnormal, means at each of said stations for conditioning said line circuit with an inferior condition during selected ones of said impulses, and means at each station responsive to said superior condition for canceling an inferior condition imposed upon said line circuit by that station.

7. In a centralized trafiic controlling system for railroads, a control office and a plurality of field stations, a line circuit connecting said office with said stations, means in the control ofiice for applying normally time spaced impulses of normal length to said line circuit, means at each of said stations for at times conditioning said line circuit with a superior condition during selected ones of said impulses and selected ones of said time spaces whereby the length of an impulse is changed from normal to abnormal and a time space between impulses is changed from normal to abnormal, means at each of said stations for at times conditioning said line circuit with an inferior condition during selected ones of said impulses and selected ones of said time spaces, and means at each station controlled by said superior condition for canceling an inferior con dition imposed upon said line circuit by that station.

8. In a centralized trafiic controlling system for railroads, a control oflice, a superior field station and an inferior field station, a single circuit line connecting said ofilce with said stations, means in said office for opening and closing said line during an operating cycle for applying uniformly time spaced impulses of uniform length thereto, means at each of said stations for opening and closing said line whereby it is distinctively conditioned for each impulse and for each time space between impulses, means effective to permit both of said stations to open and close said line during a portion of said cycle, and means controlled by the opening and closing of said line by said superior station for preventing said 

